Ammon News - Nasa’s Moon mission astronauts have travelled further from Earth than any humans in history – but the most dangerous part of their journey is yet to come.

The Orion capsule is due to re-enter Earth’s atmosphere using a trajectory that has never been tested and a heat shield that has previously failed. If all goes to plan, it will splash down in the sea off California at 17.07 EDT (22.07 BST) on Friday.

Re-entry will not be a good moment for anything to go wrong for the four Artemis II astronauts as they near the end of their 10-day, 700,000-mile journey around the Moon and back.

The 15ft-by-9ft capsule will smash, bottom first, into the atmosphere at almost 25,000mph, meaning the astronauts will be travelling at seven miles per second. Flying that fast through gas causes extreme friction and pressure, and the air around Orion will heat up to more than 2,760C.

All that will protect the astronauts from the inferno is a 3in-thick heat shield made of silica fibres and epoxy resin, housed in a fibreglass honeycomb mesh. The material is designed to disintegrate, atom by atom, in a controlled way that carries heat away from Orion.

Unfortunately, when the capsule was tested without a crew during the Artemis I mission in 2022, the disintegration was haphazard, with chunks flying off unexpectedly at more than 100 locations. Large bolts in the heat shield partially melted.

A Nasa investigation found that gases, which should have vented, built up inside the material, resulting in cracking that caused “charred material to break off”, leaving a trail of debris.

The Telegraph